1. Field of the Invention
This invention relates to an interlock device for a shift mechanism of a multi-speed power transmission device and, more specifically, to such an interlock device which will prevent shifting of the transmission when the torque transmitting power souce to the transmission device is in a power mode.
2. Description of the Prior Art
There are a number of multi-drive vehicles which utilize a main transmission and a transfer case which is capable of providing power to the rear axle alone or to both the front and rear axles at the same time. Typical transfer cases of this type are disclosed in U.S. Pat. Nos. 3,095,785; 3,557,634 and 3,679,016.
It is not uncommon in transfer cases to include a means for providing a multi-speed power transmission function in the form of ligh and low speed operation. Transfer cases such as those disclosed in U.S. Pat. Nos. 3,941,199 and 4,188,838 include such features and significantly increase the selective operating gear ratios which are available to the operator of a vehicle which uses a main transmission in conjunction with the transfer case.
However, in vehicles of this type, it is of concern that the vehicle should not be operated in a power mode when selecting high or low speed since providing a torque to the transfer case during a shifting operation might result in damage to the high or low speed gearing. Generally, without any protection means being included in the transfer case, the operator is to only shift the gears when the vehicle is at rest and no power is being transmitted to the transfer case.